Default to 11, but allow 14, even with clang
Default to 11, but allow 14, even with clang

mongodb/mongo-cxx-driver,acmorrow/mongo-cxx-driver,mongodb/mongo-cxx-driver,mongodb/mongo-cxx-driver,mongodb/mongo-cxx-driver,acmorrow/mongo-cxx-driver,xdg/mongo-cxx-driver,xdg/mongo-cxx-driver,acmorrow/mongo-cxx-driver,acmorrow/mongo-cxx-driver,xdg/mongo-cxx-driver,xdg/mongo-cxx-driver